THE MTCROSCOPIST IN BERMUDA. 123 



these spines is most remarkable. Thin transverse sections of 

 them make exceedingly beautiful objects under the microscope. 

 Rays from the center pass outward through successive rings 

 which seem to mark certain periods of growth, these all being 

 formed of the finest net-work of calcareous glass, while every 

 shade of color beautifies the pattern. I will have the pleasure 

 of showing you some of these at the close of the lecture. 



But another set of organs, not less numerous or wonderful 

 than the spines, covers the test of these animals. Alternating 

 witli the meridional segments which carry the spines, are other 

 segments pierced with minute holes. Over every two of these 

 holes there is a fleshy tube, which can be extended to a consid- 

 erable distance beyond the spines, and at the end there is a 

 sucker which can be applied to any surface, and by drawing on 

 the central part a vacuum is produced, by which the Echinus 

 pulls itself about, or climbs the rocks beneath the water. The 

 holes are for the purpose of admitting water, which the animal 

 forces into the tubes to extend them. Muscular contraction does 

 the rest of the work. Considering that there are as many as 

 five thousand of these little elephant trunks on each sea-urchin, 

 and that each of them seems to be under separate control, one 

 would think that this small animal ought to be a pretty skillful 

 operator to know just which one to extend and take hold with, 

 and which one to draw in and to loosen. Yet it never makes a 

 mistake. 



There is still another set of organs, more strange and wonder- 

 ful even than the two others. Scattered all over among the 

 spines and tube-feet, are tiny upright threads of glass, covered 

 w T ith a muscular tissue, and surmounted at the tops, each with 

 three minute prongs, toothed or spiked on the inner edges ; and 

 these triangular jaws are being continually opened and shut 

 against each other, snapping and biting without a moment's 

 pause as long as the animal lives: They were for a long time 

 supposed to be little parasites on the Echinus, and received the 

 name of pedicellarise, which is the Latin for the louse parasite. 

 They still retain the name, but are now known to be an essential 

 part of the Echinoid economy, whatever that may be ; for the 



